Eye-protective ophthalmic glass



Patented Sept. 7, 1954 EYE-PROTECTIVE OPHTHALMIC GLASS William Armistead, Corning, N. Y., assignor to Corning Glass Works, Corning, N. Y., a corporation of New York No Drawing. Application April 27, 1953, Serial No. 351,491

14 Claims. 1

This invention relates to neutral or gray-colored ophthalmic glasses having substantial absorption for infrared and ultraviolet as well as visible radiations.

Infrared and ultraviolet radiations are effectively absorbed by glasses containing FeO and FezO; respectively, and these oxides are commonly utilized in glasses for these purposes. A glass containing both FeO and F8203, melted under reducing conditions, has a greenish color which can be neutralized to gray by combination with the complementary purple color produced by NiO in glasses of the type K2O.RO.SiO2 where R is a bivalent metal of the second periodic group. The color of such a neutral glass is difiicult to control, however, because the greenish complement tends to vary objectionably in hue depending upon the extent of the reduction.

I have now discovered that the inclusion of T102 in such a glass provides control of the hue of its greenish complement and thereby of the desired neutral color, as a result of which minor variations in the reducing conditions can be readily tolerated without the production of any deleterious eifects.

The new neutral-colored glasses are reduced glasses which comprise essentially 45 to 72% S102, 14 to 23% K20, and at least one glassstabilizing oxide in the indicated proportion selected from the group consisting of up to 12% BeO, up to 15% MgO, up to CaO, but not over 20% of MgO-i-CaO, up to 35% SrO, up to CdO and up to BaO, the total oxides of such group being 6 to 35%, and contain glass-coloring components consisting of FeO and FezO: totalling 0.3% to 4.5% computed as FezOs, 0.1% to 2% T102, and i 02% to 0.50% NiO, the ratio of the computed Fezos/NiO being 5/1 to 15/1, the essential constituents totalling at least 95. Preferably, the amount of K20 does not exceed 20%.

A1203 and ZI'Oz are also glass-stabilizing oxides; and I find that these can be alternatively included as essential ingredients in the present compositions provided that the A1203 is not over 15% and the ZIOz is not over 10%.

As is well known, the other alkali metal oxides commonly used in glass-making, namely, Na2O and LizO possess a greater fluxing power than K20 and, when substituted for K20, serve to improve the meltability of the glass and to lower its softening point. (By softening point is meant that temperature at which the viscosity of a glass is 10 poises.) The color produced by mo in a glass of the above type where Nazo and/or L120 replaces part of the K20 tends towards amher or yellow, however, unless the total alkali metal oxide content is maintained relatively high. On the other hand, as such total alkali metal oxide content increases appreciably, the chemical stability of the glass tends correspondingly to decrease.

I have found, nevertheless, that NazO and/or LizO can be satisfactorily included as essential ingredients in the present reduced, neutral-colored glasses provided that the NazO- does not exceed 11%, the LizO does not exceed 4%, the total NazO and LizO is not over 11%, and the total alkali metal oxide content does not exceed 25%, and preferably 20%.

The following glass compositions calculated from their respective batches to the oxide basis in parts by weight are illustrative of my invention. (The amounts of the coloring oxide, NiO, being less than 0.50, are expressed to two significant places; but such practice is without significance in expressing the major constituents. Since the compositions total approximately, if not exactly, the amounts given for the various constituents thereof can for practical purposes be called percent by weight.)

To provide the desired greenish complementary color of the iron oxides, the batches for the present glasses are melted under reducing conditions, advantageously by introducing part of the iron oxide content into each batch as a ferrous compound, for example as ferrous oxalate, or alternatively by including in a batch containing Fezoa a small amount of starch. Since the reducing agent, for example the oxalate radical or the starch, is completely eliminated during melting of the batch, it is not included in the final compositions given above. The proportion of oxalate or starch or other reducing agent which produces the desired result will of course vary with the glass composition and/or the particular melting conditions. Less reducing agent is required for melting in a closed melting container or covered pot than for melting in an open melting container such as a tank. The exact amount of reducing agent for all conditions cannot therefore be stated, but for each condition it can readily be determined by trial. It is preferable to utilize ferrous oxalate as the reducing agent because glasses made from batches containing it fine more readily thanglasses made from batches containing starch, sugar or carbon.

Due to the fact the FeO is a stronger glasscoloring oxide than F8203, the ratio of the total iron oxides to M or the computed FezOa/NiO ratio may, without change of the neutral color, vary between /1 and 15/1, depending upon the proportionate amount of FeO relative to that of Fezoa or the extent of reduction of the glass. To decrease the ratio within such limits requires an increase in the proportionate amount of Fe0= or a stronger reduction and to increase the ratio requires a decrease in the proportionate amount of FeO or a weaker reduction. When the proportionate amount of Fe0 is thus increased the Ti02 content should be correspondingly increased to counteract the increasing bluish tendency due to the FeO and thus to maintain the desired greenish complement; and, when the proportionate amount of FeO is decreased, the T102 content should be correspondingly decreased to avoid the yellowish tendency otherwise caused by F6203 and T102.

The total iron oxide content of the glass, however, should be maintained within the limits set forth above, because an excess in the total Fe'O and Fe20s causes the general color of the glass to appear too green while a deficiency causes it to appear too red. The color due to iron is not substantially changed when the glass is tempered, that is, heated nearly to its softening point and suddenly cooled uniformly through several hundred degrees C.

With an excess of Ti02 the color of the glass tends too much towards amber and with a deficiency the color tends too much towards blue.

An excess of N causes the color of the glass to appear too purple and a deficiency of N10 causes the color to appear too green. The color due to NiO is intensified by tempering the glass; consequently, if the glass is to be tempered, the N10 content should be lowered slightly, generally on the order of about 0.02%.

It is essential that no glass-coloring oxide other than FeO, F8203, Ti02 and N10 be present in the glasses of this invention because the desired neutral color cannot otherwise be obtained.

The color of the present glasses is also influ-v enced to some extent by the selection and/or combination of certain of the other constituents. For example, the purple complement of the N10 tends to be shifted somewhat towards amber by an increasing content of BeO or Mg0 and, to a less extent, of Ca-O unless the total alkali-metal oxide content is either near the maximum or consists of K20 and is relatively high,-as'is'shown in Examples 2 and 3. Thepresence of SrO, CdO, BaO, A1203, or ZrOz in the glass within theabovestated limits has no substantial effect upon its color, on the other hand.

To maintain the desired properties of the present glasses, such as good meltability, adequate physical and chemical durability, and useful ophthalmic characteristics, the proportions of the remaining constituents should be kept within the above-stated ranges for the following reasons:

An excess of 'Si02 or A1203 or ZiOz, or an in- 4 suificiency of alkali metal oxide hardens the glass and makes it difficult to melt.

Devitrification results from an excess of S102, or from an excess of any of the oxides of the group BeO, MgO, CaO, SrO, CdO, and BaO. Moreover for the same reason, the total MgO and =Ca'0, if both are present, should not exceed 20%, and the oxides of said group should not total over 35%.

The chemical durability of the glass is lowered obj ectionably by an excess of any individual alkali metal oxide or by an excess of Na20 and LizO combined or by an excess of total alkali metal oxides, or by an insufiiciency of S102. The same difficulty is encountered if the total amount of the glass-stabilizing oxides is less than 6%.

Up to 5% of other compatible glass-forming oxides or constituents may be included in the present glasses. Because PbO in excessive amounts tends to be readily reduced to metallic lead,it should not exceed about 3%.

Glasses of the present type in which the glassstabilizing oxide is either ZnO- or 13203 are described and claimed in my copending application, Serial No. 351,492 filed concurrently herewith; and glasses of the present type in which the glass-stabilizing oxide is ZnO and which possess specifically desirable ophthalmic properties are described and claimed in my copending application, Serial No. 351,493 also filed concurrently herewith.

What is claimed is:

1. A reduced substantially neutral-colored infrared-absorbing and ultraviolet-absorbing glass comprising essentially 45 to 72% Si02, 14 to 23% K50, and at least one glass-stabilizing oxide in the indicated proportion selected from the group consisting of up to 12% BeO, up to 15% MgO, up to 20% CaO, up to 35% SrO, up to 30% CdO, up to 35% BaO, up to 15% A1203, and up to 10% ZrOz, the total MgO'and CaO not exceeding 20%, the total oxides of such group being 6 to 35%, and containing glass-coloring components consisting of FeO-and FezOs totalling 0.3 to 4.5% computed as F6203, 0.1 to 2% T102, and 0.02 to 0.50% NiO, the ratio of thecomputed FezOa/NiO being 5/1 to 15/1, the essential constituents totalling :at least 2. A reduced substantially neutral-colored infrared-absorbing and ultra-violet-absorbing glass comprising essentially 45 to 72% Si02, 14 to 20% K20, and at least one glass-stabilizing oxide in the indicated proportion selected from the group consisting of up to 12% BeO, up to 15% MgO, up to 20% CaO, up to 35% $10, up to 30% CdO, up to 35% 1320, up to 15% A1203, and up to 10% mm, the total MgO and CaO not exceeding 20%., the total oxides of such group being '6 to 35%, and containing glass-coloring components consisting of Fe'O and Fe203 totalling 0.3 to 4.5% computed as FezOs, 0.1 to 2% T102, and 0.02 to 0.50% NiO, the ratio of the computed Fe2'0z/Ni0 being 5/1 to 15/1, the essential constituents totalling at least 95%.

3. A glass as claimed in claim 2 in which the selected glass-stabilizing oxide is 'CaO.

4. A glass as claimed in claim 2, which includes at least two glass-stabilizing oxides, said oxides :being MgO and CaO.

5. A glass as claimed in claim 2 in which the selected glass-stabilizing oxide is BaO.

6. A glass as claimed in claim 2 in which the selected glass stabilizing oxide is A1203.

7. .A reduced substantially neutral-colored inflared-absorbing and ultraviolet-absorbing glass comprising essentially 45 to 72% Si02, 14 to 23% K20, at least one alkali metal oxide in the indicated proportion selected from the group consisting of up to 11% N220 and up to 4% Li20, the total percentage of Na20 and Li20 being not over 11%, the total alkali metal oxides being not over 25%, and at least one glass-stabilizing oxide in the indicated proportion selected from the group consisting of up to 12% BeO, up to 15% MgO, up to 20% 020, up to 35% SrO, up to 30% CdO, up to 35% BaO, up to 15% A1203, and up to% Zr02, the total MgO and CaO not exceeding 20%, the total oxides of such group being 6 to 35%, and containing glass-coloring components consisting of FeO and F6203 totalling 0.3 to 4.5% computed as E5203, 0.1 to 2% Ti02, and 0.02 to 0.50% NiO', ratio of the computed Fezoa/Nio being 5/1 to /1, the essential constituents totalling at least 95%.

8. A reduced substantially neutral-colored inflared-absorbing and ultraviolet-absorbing glass comprising essentially 45 to 72% S102, 14 to K20, at least one alkali metal oxide in the indicated proportion selected from the group consisting of up to 11% Na20 and up to 4% L120, the total percentage of Na20 and Li20 being not over 11%, the total alkali metal oxides being not over 20%, at least one glass-stabilizing oxide in the indicated proportion selected from the group consisting of up to 12% BeO, up to 15% MgO, up to 20% CaO, up to 35% SrO, up to 30% CdO, up to 35% BaO, up to 15% A1203, and up to 10% Zr02, the total MgO and CaO' not exceeding 20%, the total oxides of such group being 6 to 35%, and containing glass-coloring components consisting of FeO- and Fe203 totalling 0.3 to 4.5% computed as Fe20s, 0.1 to 2% Ti02 and 0.02 to 0.50% M0, the ratio of the computed Fe203/Ni0 being 5/1 to 15/1, the essential constituents totalling at least 95%.

9. A glass as claimed in claim 8 in which the selected glass-stabilizing oxide is CaO.

10. A glass as claimed in claim 8, which ineludes at least two glass-stabilizing oxides, said oxides being MgO and CaO.

11. A glass as claimed in claim 8 in which the selected glass-stabilizing oxide is BaO.

12. A glass as claimed in claim 8 in which the selected glass-stabilizing oxide is A1203.

13. A reduced substantially neutral-colored inflared-absorbing and ultraviolet-absorbing glass consisting essentially of to 72% Si02, 14 to 20% K20, and at least one glass-stabilizing oxide selected from the group consisting of up to 12% BeO, up to 15% MgO, up to 20% CaO, up to 35% SrO, up to 30% CdO, up to 35% BaO, up to 15% A1202, and up to 10% Zr02, the total MgO and Ca0 not exceeding 20%, the total oxides of such group being 6 to 35%, and containing glass-coloring components consisting of FeO and Fe2O3 totalling 0.3 to 4.5% computed as FezOs, 0.1 to 2% T102 and 0.02 to 0.50% N10, the ratio of the computed Fe203/Ni0 being 5/1 to 15/1.

14. A reduced substantially neutral-colored infrared-absorbing and ultraviolet-absorbing glass consisting essentially of 45 to 72% S102, 14 to 20% K20, at least one alkali metal oxide in the indicated proportion selected from the group consisting of up to 11% Na20 and up to 4% Li20, the total percentage of Na20 and U20 being not over 11%, the total alkali metal oxides being not over 20%, and at least one glassstabilizing oxide selected from the group consisting of up to 12% BeO, up to 15% MgO, up to 20% C'a0, up to 35% $10, up to 30% 06.0, up to 35% BaO, up to 15% A1203, and up to 10% ZrO2, the total MgO and CaO not exceeding 20%, the total oxides of such group being 6 to 35%, and containing glass-coloring components consisting of FeO and R203 totalling 0.3 to 4.5% computed as Fe2O3, 0.1 to 2% T102, and 0.02 to 0.50% M0, the ratio of the F'e203/Ni0 being 5/1 to 15/1.

No references cited. 

1. A REDUCED SUBSTANTIALLY NEUTRAL-COLORED INFRARED-ABSORBING AND ULTRAVIOLET-ABSORBING GLASS COMPRISING ESSENTIALLY 45 TO 72% SIO2, 14 TO 23% K2O, AND AT LEAST ONE GLASS-STABILIZING OXIDE IN THE INDICATED PROPORTION SELECTED FROM THE GROUP CONSISTING OF UP TO 12% BEO, UP TO 15% MGO, UP TO 20% CAO, UP TO 35% SRO, UP TO 30% CDO, UP TO 35% BAO, UP TO 15% AL2O3, AND UP TO 10% ZRO2, THE TOTAL MGO AND CAO NOT EXCEEDING 20%, THE TOTAL OXIDES OF SUCH GROUP BEING 6 TO 35%, AND CONTAINING GLASS- COLORING COMPONENTS CONSISTING OF FEO AND FE2O3 TOTALLING 0.3 TO 4.5% COMPUTED AS FE2O3, 0.1 TO 2% TIO2, AND 0.02 TO 0.50% NIO, THE RATIO OF THE COMPUTED FE2O3/NIO BEING 5/1 TO 15/1, THE ESSENTIAL CONSTITUENTS TOTALLING AT LEAST 95%. 